Present LED strips can be bent easily in one direction, see for example the stepwise curved lamp unit in FIGS. 1 and 2 of US 2011/0228536 (Im et al.). However, perpendicular to this direction one cannot bend the strip without running the risk of ruining the copper tracks. So, installing the strip goes well as long as the strip has to curve in one direction only.
In US 2015/0354797 a flexible circuit board is disclosed for an illumination device. The flexible circuit board includes a plurality of mounting sections for the LEDs and connection sections for mutual connecting adjacent mounting sections, so forming a longitudinal lighting device. The connection sections forming a predetermined angle in the longitudinal direction with respect to the mounting sections.